calvol

Sedan = .27 (coefficient of drag)
Coupe = .29
330i = .31

The Coupe front looks sleeker than the Sedan, but has a higher CoD. Maybe the "bubble butt" of the Coupe causes more drag?

dswildfire

the increase in drag isn't so much the bubble butt as the loss of the smooth line of the roof. if you look slightly past halfway on the roofline (coming from the front), you can see where the curvature leaves the sedan profile and becomes the coupe's, that slight change is what causes an increase in drag.

as for the 330, i don't know, it does have a fairly boxy front end, so that could be the cause. and i dont know if the 330 has a smoothe underbody (although i doubt it wouldn't) which could also be the cause.

Mike T.

You'll need to know the frontal surface area of these three cars in order to gain real insight into their relative aerodynamic efficiency. The S of the sportcoupé is apparently a wee bit less than the sedan, though probably not enough to make up for its inferior Cd. Lift coefficients on the front and rear axles would also be useful information

Apollo

Maybe this is why I seem to have a lot of stone chips on my sedan bonnet.

vadim

Don't forget that the coupe is short and has a little spoiler to provide the necessary downforce to the rear axle. This - along with its sharply cut back- results in increased turbulence right behind its tail, which means - higher drag coefficient.

Rick

Are you saying the coupe is draggin' azz?

mdp c230k

The little curvature on the edge of the rear deck of the coupe is supposed to increase the rear down force which will also increase the Cd.